Omega-hydrofluoroalkyl ethers, precursor carboxylic acids and derivatives thereof, and their preparation and application

ABSTRACT

Normally liquid, omega-hydrofluoroalkyl ether compounds (and selected mixtures thereof) have a saturated perfluoroaliphatic chain of carbon atoms interrupted by one or more ether oxygen atoms. The compounds can be prepared, e.g., by decarboxylation of the corresponding fluoroalkyl ether carboxylic acids and are useful, e.g., in cleaning and drying applications.

This is a division of application Ser. No. 09/151,857 filed Jun. 11,1998, which was a division of application Ser. No. 08/881,347 filed Jun.24, 1997, which was a division of application Ser. No. 08/440,450 filedMay 12, 1995, now U.S. Pat. No. 5,658,962. which was acontinuation-in-part of application Ser. No. 08/246,962 filed May 20,1994, now U.S. Pat. No. 5,476,974.

This invention relates to omega-hydrofluoroalkyl ethers and theirpreparation and application. In another aspect, this invention relatesto perfluoro(alkoxyalkanoic) acids and derivatives thereof and theirpreparation. In another aspect, it relates to the preparation ofperfluoro(alkoxyalkanoic) acids by direct fluorination of theirhydrocarbon alkanoic acid or ester analogs and to the preparation ofomega-hydrofluoroalkyl ethers, for example, by decarboxylation of saidacids or their alkyl esters. In another aspect, this invention relatesto uses of perfluoro(alkoxyalkanoic) acids and derivatives thereof.

Because of a steady flow of bad news about the damaged stratosphericozone layer, the deadlines for the end to industrialized countries'production of chlorofluorocarbons (“CFCs”) and other ozone-depletingchemicals were accelerated by countries who are parties to the MontrealProtocol on Substances That Deplete the Ozone Layer—see Zurer, P. S.,“Looming Ban on Production of CFCs, Halons Spurs Switch to Substitutes,”Nov. 15, 1993, Chemical & Engineering News, p. 12.

Work is under way to replace CFCs and halons, such as CCl₂F₂, CCl₃F,CF₃Br, and CCl₂FCClF₂, with substitute or alternative compounds andtechnologies. A number of hydrofluorocarbons (“HFCs”), e.g., CH₂FCF₃(“HFC-134”), are being used or have been proposed as CFC substitutes(and HFC-134a has been characterized as being more “ozone friendly”—seeU.S. Pat. No. 5,118,494 (Schultz et al.)). Hydrochlorofluorocarbons(“HCFCs”), such as CH₃CCl₂F (“HCFC-141b), as the C&EN article, supra,points out, are CFC substitutes, but although they are not nearly asdamaging, these substitutes do carry ozone-depleting chlorine into thestratosphere. Another proposed substitute is the simpleomega-hydrodifluoromethyl perfluoromethyl ether, CF₃OCF₂H—See J. LAdcock et. al., “Fluorinated Ethers—A new Family of Halons,” 1991 CFCConference Proceedings (1991). Another hydro-fluoroalkyl ether (or etherhydride), F[CF(CF₃)CF₂O]₄CFHCF₃, made by decarboxylation of thefluorinated 2-alkoxypropionic acid salt, has been tested as a bloodemulsion—see Chem. Pharm. Bull. 33, 1221 (1985).

U.S. Pat. No. 4,173,654 (Scherer) states that fluorocarbons due to theirinertness have found use as electronic coolant or leak testing fluids,and other compounds having good solubility for oxygen have beeninvestigated as artificial blood substitutes. This patent describescertain fluorocarbon “hybrid” materials with metabolically activehydrocarbon moieties, such as, inter alia, —CH₂—(CH₂)_(m)—H. U.S. Pat.No. 4,686,024 (Scherer et al.), which describes certain perfluorocyclicethers, states that various perfluoro chemicals are disclosed in patentsas being suitable as oxygen and carbon dioxide carriers. AndInternational Application published as WO 93/11868 (Kaufman et al.)describes certain chlorofluorochemicals and emulsions thereof as usefulin various oxygen transport applications, e.g., as oxygen transferagents or “artificial bloods.”

There are a number of other patents describing various fluorocarbonethers or polyethers. U.S. Pat. No. 3,342,875 (Selman et al.) describescertain “hydrogen modified fluorocarbon ethers” (or “hydrogen cappedpolyethers”) made, inter alia , by pyrolysis of a hydrogen-containingderivative of an ether, such as the fluorocarbon ether acid or theammonium salt, which ether is obtained by the polymerization offluorocarbon epoxides. British Patent Specification 1,194,431(Montecatini Edison S.P.A.) describes certain perfluorinated ethers andpolyether derivatives having the general formula

CF₃—O—(C₃F₆O)_(M)—(CF₂O)_(N)—(CF(CF₃)—O)_(L)—CF₂X

where, inter alia, each subscript M, N, and L is zero or a whole numberfrom 1 to 99, and X is a hydrogen atom or —COOMe wherein Me is anequivalent of an alkali or alkaline earth metal, an examples of which ispentafluorodimethyl ether, CF₃—O—CF₂H.

U.S. Pat. No. 3,597,359 (Smith) describes certain perfluoroalkyleneether-containing compound represented by the formula

wherein, inter alia, R is alkylene, alkoxyalkylene, orperfluoroalkylene, R₁ is fluorine or trifluoromethyl provided not morethan one R₁ is trifluoromethyl, R₂ is fluorine or trifluoromethylprovided not more than one R₂ is trifluoromethyl, R₃ is fluorine ortrifluoromethyl, R₄ is hydrogen or halogen provided that when R isalkylene or alkoxyalkylene R₄ is hydrogen, R₅ is perfluoroalkylenehaving at least 2 carbon atoms, R₆ is, inter alia hydrogen,trifluoromethyl or perfluoroethyl, a is zero or 1, n and m are wholenumbers of 0 to 50, and n+m is 1 to 50.

U.S. Pat. No. 3,962,460 (Croix et al.) describes aliphatic ethers,including those of the formulas

International Patent Application WO 90/01901 (Long) describes certainperfluorocarbon hydrides, such as perfluorooctyl hydride, used inemulsions for carrying oxygen to the tissues of an animal body. EuropeanPatent Application Publication No. 0 482 938 A1 (Chambers et al.)describes fluorinated ethers of the formula

wherein R is hydrogen, fluorine, or alkyl or fluoroalkyl of 1-6 carbonatoms, R′ is hydrogen or alkyl or fluoroalkyl of 1 to 6 carbon atoms,and R″ is fluorine or alkyl or fluoroalkyl of 1 to 6 carbon atoms.

Other patents describing one or more various fluoroalkoxyalkanoic acidsand esters or other derivatives thereof and their preparation are U.S.Pat. No. 2,713,593 (Brice et al.), U.S. Pat. No. 3,214,478 (Milian,Jr.), U.S. Pat. No. 3,393,228 (Braun), U.S. Pat. No. 4,118,421(Martini), U.S. Pat. No. 4,357,282 (Anderson et al.), U.S. Pat. No.4,729,856 (Bernonge), U.S. Pat. No. 4,847,427 (Nappa), U.S. Pat. No.4,940,814 (Schwertfeger), U.S. Pat. No. 4,973,716 (Calini et al.), U.S.Pat. No. 5,053,536 (Bierschenk et al.) U.S. Pat. No. 5,093,432(Bierschenk et al.), and U.S. Pat. No. 5,118,494 (Schultz et al.) andPCT International Applications Pub. Nos. WO 90/03357 (Moore et al.) andWO 90/06296 (Costello et al.). The aforementioned Brice et al. patentdescribes fluorocarbons acids made by electrochemical fluorinationincluding an acid having a boiling point of 225° C. and said to ben-C₈F₁₇OC₂F₄CO₂H. The aforementioned Nappa, Bierschenk et al., Moore etal., and Costello et al. publications describe the preparation of thefluorinated compounds by direct fluorination of hydrocarbon analogprecursors.

In one aspect, this invention provides a normally liquid (i.e., liquidunder ambient conditions of temperature and pressure) fluoroalkyl ethercompound or a normally liquid composition consisting or consistingessentially of a selected mixture of such compounds, said compoundhaving a saturated perfluoroaliphatic chain of carbon atoms (e.g., 4 to30) interrupted by one or a plurality (e.g., 2 to 8) of ether (orcatenary, i.e., in-chain) oxygen atoms. The chain carbon atom at one end(hereafter called the proximal end) of the chain is bonded to a hydrogenatom (i.e., an omega-hydro substituent, or primary hydrogen atom) andtwo fluorine atoms, said proximal carbon atom being the carbon atom of adifluoromethyl group or moiety, —CF₂H, which is directly bonded toanother chain carbon atom, such as that of perfluoroalkylene chainsegment, —C_(N)F_(2N), or to a said ether-oxygen. The carbon atom at theother end of the chain (the distal end) is part of a distal groupselected from the group consisting of a difluoromethyl, adifluorochloromethyl, —CF₂Cl, a perfluoroalkyl substituted with asaturated alicyclic moiety, e.g., c—C₆F₁₁—, a straight-chainperfluoroalkyl, and a branched chain perfluoroalkyl. In a said compoundwhere said proximal end of the chain terminates in a difluoromethylgroup bonded to an ether-oxygen atom, then said straight-chainperfluoroalkyl has at least 6 chain carbon atoms, e.g., 6 to 16 chaincarbon atoms, and said branched-chain perfluoroalkyl has at least 4carbon atoms, e.g., 4 to 16 carbon atoms. Examples of such omega-hydrofluoroalkyl ether compounds are:

 CF₃(CF₂)₄—O—CF₂CF₂H

CF₃(CF₂)₅—O—CF₂H

CF₃(CF₂)₇—O—(CF₂)₅H

CF₃(CF₂)₅—O—(CF₂)₂—O(CF₂)₂H

H(CF₂)₂—O—(CF₂)₂H

Cl(CF₂)₄—O—(CF₂)₄H

If a said “selected mixture,” i.e., a predetermined mixture of selectedomega-hydrofluoroalkyl ether compounds, is desired for a particular use,a said composition of this invention can be made consisting orconsisting essentially of a mixture of two or more of said compoundseach having a desired discrete, non-random molecular weight, theselected compounds preferably being those having complementaryproperties, e.g., for imparting improved stability to emulsions wherethey are incorporated as oxygen carriers in medical applications.

The term “perfluoro,” such as in the case of “perfluoroaliphatic, ”“perfluoroalkylene,” or “perfluoroalkyl,” means that except as may beotherwise indicated there are no carbon-bonded hydrogen atomsreplaceable with fluorine nor any unsaturation.

Omega-hydrofluoroalkyl ethers of this invention are hydrophobic and lessoleophobic than the perfluoroalkyl ether analogs, chemically inert,thermally stable, water insoluble, and normally liquid (e.g., at 20°C.), and they can be made in accordance with this invention in highyield, high purity, and with a wide range of molecular weights. Thecovalent bond between the omega-hydrogen and terminal carbon, i.e., theC—H bond, is generally degradable by atmospheric photo-oxidation, thusmaking the omega-hydrofluoroalkyl ethers environmentally acceptable orcompatible. The omega-hydrofluoroalkyl ether compounds, or the normallyliquid composition consisting or consisting essentially thereof, can beused in applications where the aforementioned CFCs, HCFCs or halons havebeen used, for example, as solvents for precision or metal cleaning ofelectronic articles such as disks or circuit boards, heat transferagents, coolants in refrigerator or freezer compressors or airconditioners, blowing agents or cell size regulators in makingpolyurethane foam insulation, or chemical fire extinguishing agents instreaming applications, total flooding, explosion suppression andinertion, and as carrier solvents for highly fluorinated polyethers usedas lubricants for magnetic recording media. Another field of utility forthe omega-hydrofluoroalkyl ethers is in emulsions useful in variousmedical and oxygen transport applications, for example, artificial orsynthetic bloods.

The above-described omega-hydrofluoroalkyl ethers of this invention canbe prepared by decarboxylation of the corresponding precursorfluoroalkyl ether carboxylic acids and salts thereof or, preferably, thesaponifiable alkyl esters thereof. Alternatively, theomega-hydrofluoroalkyl ethers can be prepared by reduction of thecorresponding omega-chlorofluoroalkyl ethers (e.g., those described inWO 93/11868, supra). The perfluoroalkyl ether carboxylic acids (andesters) themselves—some of which are believed novel compounds and theyand their preparation are other aspects of this invention—can beprepared by direct fluorination of their corresponding hydrocarbonanalogs. The omega-hydrofluoroalkyl ethers are essentially purefluorinated compounds and are useful as such or in the form of anormally liquid composition consisting or consisting essentially of aselected mixture of such compounds. The precursor perfluoroalkyl ethercarboxylic acid and ester compounds, like the above-describedomega-hydrofluoroalkyl compounds of this invention, have a saturatedperfluoroaliphatic chain of a plurality of carbon atoms, said chainlikewise being interrupted by one or a plurality of ether oxygen atoms,the proximal end of the chain being connected to a carboxyl group oralkyl ester thereof. This carboxyl group (or salts thereof or itssaponifiable alkyl ester) can be decarboxylated, as mentioned above, andthereby replaced by the aforementioned omega-hydro substituent of theresulting omega-hydroalkyl ether of this invention.

The aforementioned novel perfluoroalkyl ether acids and esters can alsobe converted into various other derivatives, such as their ammoniumsalts, which have utility as surface active agents useful in modifyingthe surface tension or interfacial tension of liquids. These compoundsare more soluble in aqueous media and other organic solvents than arethe corresponding perfluoroalkanoic acid derivatives, and this enhancestheir utility as surface-active agents. The compounds can convenientlybe prepared by direct fluorination of the corresponding hydrocarbonether acids, or derivatives such as an ester, in high yields as singlemolecular species.

A class of the normally liquid, omega-hydrofluoroalkyl ether compoundsof this invention can be represented by the general formula:

X—R_(f)—O—(R_(f)′—O)_(n)—R_(f)″—H  I

wherein:

H is a primary hydrogen atom;

X is a fluorine atom, a primary hydrogen atom, or a primary chlorineatom bonded to a difluoromethylene (of R_(f));

n is a integer of 0 to 7, preferably 0 to 3;

R_(f), R_(f)′, and R_(f)″ are the same or different perfluoroalkylene(linear or branched) groups, e.g., —CF₂CF₂—, which are unsubstituted orsubstituted with a perfluoro organo group which can contain etheroxygen, for example, R_(f) can be —CF₂CF(R_(f)′″)CF₂— or —R_(f)′″CF₂—where R_(f)′″ is a saturated perfluoroalicyclic group having 4 to 6 ringcarbon atoms, such as perfluorocyclohexyl or perfluorocyclohexylene;

with the proviso that when X is H or Cl, R_(f) has 1 to 18, preferably 2to 18, chain carbon atoms, R_(f)′ has 1 to 12, preferably 2 to 12, chaincarbon atoms, and R_(f)″ has 2 to 12 chain carbon atoms;

and with the further proviso that when X is F, then R_(f) has at least4, preferably 4 to 18, chain carbon atoms, R_(f)′ has 1 or more,preferably 1 to 12, more preferably 2 to 12, chain carbon atoms, andR_(f)″ has 2 or more, preferably 2 to 12, chain carbon atoms.

A subclass of polyether compounds within the scope of general formula Iis represented by the general formula:

X—R_(f)—O—(CF₂CF₂—O)_(m)—R_(f)″—H  II

where m is an integer of 0 to 7, and H, X, R_(f), and R_(f)″ are asdefined for formula I.

Another subclass of compounds within the scope of general formula I isrepresented by the general formula:

F—R_(f)—O—(R_(f)′—)_(p)—R_(f)″—H  III

where p is an integer of 0 to 2 and H, R_(f), R_(f)′, and R_(f)″ are asdefined for formula I, except R_(f) has 4 to 12 chain carbon atoms,R_(f)′ has 1 to 12 chain carbon atoms, and R_(f)″ has 2 to 12 chaincarbon atoms.

Another class of the normally liquid, omega-hydrofluoroalkyl ethercompounds of the invention can be represented by the general formula:

X—R_(f)—OR_(f)′—O_(n)R_(f)″—H

wherein:

H is a primary hydrogen atom;

X is a fluorine atom, a primary hydrogen atom, or a primary chlorineatom;

n is an integer of 0 to 7; and

R_(f), R_(f)′, and R_(f)″ are independently selected from the groupconsisting of linear or branched, unsubstituted perfluoroalkylenegroups; linear or branched, perfluoroalkyl- orperfluorocycloalkyl-substituted perfluoroalkylene groups; and linear orbranched perfluoroalkylene groups substituted with an etheroxygen-containing moiety;

with the proviso that when X is H or Cl, R_(f) has 1 to 18 chain carbonatoms and each of R_(f)′ and R_(f)″ independently has 1 to 12 chaincarbon atoms;

and with the further proviso that when X is F, then R_(f) has at least 4chain carbon atoms and each of R_(f)′ and R_(f)″ independently has 1 ormore chain carbon atoms;

and with the still further proviso that when n is zero, then R_(f) is aperfluorocycloalkyl-substituted perfluoroalkylene group.

A list of representative examples of the omega-hydrofluoroalkyl ethercompounds of this invention is as follows.

TABLE A 1. CF₃(CF₂)₅-O-CF₂H 2. CF₃(CF₂)₃-O-(CF₂)₂H 3.c-C₆F₁₁CF₂-O-(CF₂)₂H 4. CF₃(CF₂)₃-O-CF₂C(CF₃)₂CF₂H 5. (CF₃)₂CFCF₂-O-CF₂H6. CF₃(CF₂)₄-O-(CF₂)₅H 7. CF₃(CF₂)₆-O-CF₂H 8. CF₃(CF₂)₅-O-(CF₂)₂H 9.CF₃(CF₂)₅-O-(CF₂)₃H 10. CF₃(CF₂)₆-O-(CF₂)₂H 11. CF₃(CF₂)₇-O-CF₂H 12.CF₃(CF₂)₇-O-(CF₂)₅H 13. CF₃(CF₂)₇-O-(CF₂)₆H 14.CF₃(CF₂)₅-O-(CF₂)₂-O-CF₂H 15. CF₃(CF₂)₅-O-(CF₂)₂-O-(CF₂)₂H 16.H-(CF₂)₂-O-(CF₂)₂H 17. H-(CF₂)₄-O-(CF₂)₄H 18.H-(CF₂)₂-O-(CF₂)₂-O-(CF₂)₂H 19. H-CF₂-O-CF₂C(CF₃)₂CF₂-O-CF₂H 20.Cl(CF₂)₄-O-(CF₂)₄H 21. H(CF₂)₂OCF₂C(CF₃)₂CF₂O(CF₂)₂H 22. C₈F₁₇OCF₂OC₃F₆H23. (CF₃)₃COC₂F₄OCF₂OC₂F₄OCF₂H

As mentioned above, the omega-hydrofluoroalkyl ether compounds orcompositions of this invention can be made by decarboxylation of theircorresponding precursor perfluoroalkyl ether carboxylic acids,hydrolyzable carboxylic acid derivatives, or hydrolyzable precursorsthereto (some of which are believed novel). A class of such precursorcompounds can be represented by the general formula:

R_(fp)—OR_(f)′O_(n)R_(f)″—Z′  IV

wherein

R_(fp) is ROC(O)R_(f) or F-R_(f), R_(f) being a perfluoroalkylene groupas defined for formula I;

R_(f)′ and R_(f)″ are also perfluoroalkylene groups as defined forformula I;

n is also as defined for formula I; and

Z′ is a CO₂H, CO₂R, COF, COCl, CONR¹R², or —CF₂OC(O)R_(f), where R isselected from the group consisting of hydrogen, alkyl (such as a loweralkyl group of 1 to 6 carbon atoms), cycloalkyl, fluoroalkyl, and aryl,and where R¹ and R² are independently selected from the group consistingof hydrogen, alkyl, cycloalkyl, and heteroatom-containing cycloalkyl.

In the decarboxylation of the compounds of formula IV, the moiety Z′ isreplaced by a hydrogen atom.

Subclasses of said ether acids and derivatives thereof, which have otherutilities in addition to their use as precursors of the omega-hydroether compounds of this invention, for example, as surface active agents(or surfactants), as mentioned above, and which are believed novel, canbe represented by the general formulas V, VI, VII, VIII and IX below,

R_(fo)—O—R_(fo)′—Z  V

wherein:

R_(fo) is a perfluoroalkyl group (linear or branched) having, forexample, 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms,

R_(fo)′ is a perfluoroalkylene group (linear or branched) having, forexample, 2 to 11 carbon atoms, at least one of R_(fo) and R_(fo)′ havingat least 8 chain carbon atoms; and

Z is —COOH, —COOM_(I/v), —COONH₄, —COOR, —CH₂OH, —COF, —COCl, —CR,—CONRR, —CH₂NH₂, —CH₂NCO, —CN, —CH₂OSO₂R, —CH₂OCOR, —CH₂OCOCR═CH₂, —CONH(CH₂)_(m)Si(OR)₃, or —CH₂O(CH₂)_(m)Si(OR)₃, where M is an ammoniumradical or a metal atom having a valence “v” of 1 to 4, such as Na, K,Ti, or Al, and each R is independently an alkyl (e.g., with 1 to 14carbon atoms) or cycloalkyl, which groups can be partially or fullyfluorinated, or an aryl (e.g., with 6 to 10 ring-carbon atoms), any ofwhich groups can contain heteroatom(s), and m is an integer of 1 toabout 11.

R_(fq)O—CF₂CF₂_(a)OCF₂—Z  VI

wherein:

R_(fq) is a perfluoroalkyl group (linear or branched) having from about6 to about 18 carbon atoms, preferably 6 to 12 carbon atoms,

subscript a is an integer of at least 2, preferably 3 to 7, but when ais 2, then R_(fq) has at least about 8 carbon atoms; and

Z is as defined for formula V.

R_(fr)—O—CF₂—O—R_(fr)′—Z  VII

wherein:

R_(fr) is a perfluoroalkyl group (linear or branched) having, forexample, 2 to 18 carbon atoms, preferably 4 to 12 carbon atoms;

R_(fr)′ is a perfluoroalkylene group (linear or branched) having, forexample, 1 to 11 carbon atoms and preferably 1 to 5 carbon atoms; and

Z is as defined for formula V; and the sum of the number of carbon atomsin the groups R_(fr) and R_(fr)′ is at least about 7.

R_(fs)—OCF₂_(b)—Z  VIII

wherein:

R_(fs) is a perfluoroalkyl group (linear or branched) having, forexample, 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms;

b is an integer of at least 3, preferably 3 to 11; and

Z is as defined for formula V.

R_(ft)—(O—R_(ft)′)_(c)—O—(CF₂)_(d)—Z  IX

wherein:

R_(ft) is a perfluoroalkyl group (linear or branched) having, forexample, 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms;

R_(ft)′ is a perfluoroalkylene group (linear or branched) having, forexample, 1 to 11 carbon atoms, preferably 2 to 4 carbon atoms;

c is an integer of at least 1, preferably 1 to 4;

d is an integer of 3 or greater, preferably 3 to 9; and

Z is as defined for formula V.

The carboxylic acids of formulas V to IX are useful intermediates forthe preparation of many of the other derivatives of formulas V to IX.These derivatives include nonfunctional or functional derivatives suchas, for example, carboxylic acids, salts, esters, amides, nitrites,alcohols, acrylates, and vinyl ethers. Various patents describeprocesses for the preparation of a host of functional derivatives ofoxyperfluoroalkylene compounds, i.e., perfluoropolyethers, e.g., seeU.S. Pat. No. 3,250,808 (Mitsch et al.) and U.S. Pat. No. 4,094,911(Moore et al.), which descriptions are incorporated herein. Thesederivatives have utility for various applications, such as surfactants,elastomers, coatings, lubricants, substances used in the preparation ofliquid crystal materials such as those in U.S. Pat. No. 5,262,082(Janulis et al.), and in the treatment of fibrous substrates to impartoil and water repellency thereto. The ammonium salts of the carboxylicacid derivatives are particularly useful as surfactants.

The carboxylic acid compounds of formula V are normally solid. Thecarboxylic acid compounds of formulas VI, VII, VIII and IX generally arenormally liquid and normally liquid compositions can be made up whichconsist or consist essentially of selected mixtures of such compounds.

A list of representative examples of fluoroalkylether acids (orderivatives) which can be utilized to prepare omega-hydrofluoroalkylethers of this invention is as follows:

TABLE B 1. CF₃(CF₂)₇-O-CF₂CO₂H 2. CF₃(CF₂)₁₁-O-CF₂CO₂H 3.CF₃(CF₂)₆-O-C₂F₄CO₂H 4. CF₃(CF₂)₄-O-C₂F₄CO₂H 5. CF₃(CF₂)₅-O-C₂F₄CO₂H 6.CF₃(CF₂)₈-O-C₂F₄CO₂H 7. CF₃(CF₂)₇-O-C₂F₄CO₂H 8. CF₃(CF₂)₉-O-C₂F₄CO₂H 9.CF₃(CF₂)₁₁-O-C₂F₄CO₂H 10. CF₃(CF₂)₅-OC₂F₄O-C₂F₄CO₂H 11.C₈F₁₇-O-(CF₂)₅CO₂H 12. C₁₀F₂₁-O-(CF₂)₅CO₂H 13. CF₃-O-(CF₂)₇CO₂H 14.C₂F₅-O-(CF₂)₇CO₂H 15. C₃F₇-O-(CF₂)₇CO₂H 16. CF₃-O-(CF₂)_(9CO) ₂H 17.CF₃-O-(CF₂)₁₀CO₂H 18. CF₃(CF₂)₅-O-C₂F₄-O-C₂F₄-O-C₂F₄-O-CF₂CO₂H 19.CF₃(CF₂)₇-O-C₂F₄-O-C₂F₄-O-C₂F₄-O-CF₂CO₂H 20.CF₃(CF₂)₉-O-C₂F₄-O-C₂F₄-O-C₂F₄-O-CF₂CO₂H 21.CF₃(CF₂)₁₁-O-C₂F₄-O-C₂F₄-O-C₂F₄-O-CF₂CO₂H 22.CF₃(CF₂)₁₁-(OC₂F₄)₁₋₅-O-CF₂CO₂H from Brij^(tm)30 acetate 23.C₆F₁₃OCF₂₀(CF₂)₅CO₂H 24. CF₃(CF₂)₇-O-CF₂-O-CF₂CO₂H 25.CF₃(CF₂)₇-O-CF₂-O-C₃F₆CO₂H 26. (CF₃)₃COC₂F₄OCF₂OC₂F₄CO₂H 27.C₄F₉-O-(CF₂)₃CO₂H 28. C₅F₁₁-O-(CF₂)₃CO₂H 29. C₆F₁-O-(CF₂)₃CO₂H 30.C₅F₁₁-O-(CF₂)₄CO₂H 31. CF₃-O-(CF₂)₅CO₂H 32. C₄F₉-O-(CF₂)₅CO₂H 33.C₅F₁₁-O-(CF₂)₅CO₂H 34. C₄F₉-O-C₄F₈-O(CF₂)₃CO₂H 35.C₆F₁₃-O-C₄F₈-O(CF₂)₃CO₂H 36. C₄F₉-O-C₂F₄O-C₂F₄O(CF₂)₃CO₂H 37.CF₃-O-(C₂F₄O)₃-(CF₂)₃CO₂H 38. C₈F₁₇OCF₂OC₅F₁₀CO₂H 39.(CF₃)₃COC₂F₄OCF₂OC₂F₄OCF₂CO₂H 40. (CF₃)₂CFCF₂CF₂O(CF₂)₅CO₂H 41.CF₃(CF₂)₇OC₂F₄OC₂F₄OCF₂CO₂H 42. CF₃(CF₂)₁₁OC₂F₄OC₂F₄OCF₂CO₂H

The following presents overall schemes of reactions that can be used inthe preparation of omega-hydrofluoroalkyl ethers of this invention usinggeneral formulas defined above. In these schemes, the illustratedreaction results in the product whose formula is depicted on thesucceeding line

The ether alpha and omega dihydrides, that is, where X in formula I isH, may be prepared by analogous schemes. For example, the followingScheme IV is analogous to Scheme I

Looking first at Scheme I above, in the direct fluorination, step “a”, afluorinatable precursor ether carboxylic acid ester, e.g.,C₄H₉—O—(CH₂)₅COOCH₃, is directly fluorinated by contact with fluorinegas. (The term “fluorinatable” means that the precursor containscarbon-bonded hydrogen atoms which are replaceable with fluorine and theprecursor may contain unsaturation which can be saturated withfluorine.) The resulting fluorinated ether acid ester compound, depictedin step b, can be made with essentially the same number and spatialarrangement of carbon and oxygen atoms as the precursor thereof. If afluorinated ether acid composition which consists or consistsessentially of a selected mixture of fluorinated ether compounds isdesired, a selected mixture of the corresponding precursor compounds canbe fluorinated or, alternatively, the selected precursor compounds canbe separately fluorinated and then blended.

The direct fluorination of the fluorinatable ether precursor can becarried out at temperatures typically used in direct fluorination, e.g.,at moderate or near ambient temperatures such as −20° C. to +50° C.,using a stoichiometric excess of fluorine gas, which is preferablydiluted with an inert gas, such as nitrogen, to minimize or avoid thehazards of pure fluorine gas and to control the amount of heat generatedupon contact of the precursor with fluorine. The fluorination ispreferably carried out in an oxygen- and water-free environment and canbe carried out in the presence of solid, particulate scavenger, e.g.,sodium fluoride, for the hydrogen fluoride by-product generated. Liquidphase direct fluorination can be employed and involves using an inertliquid, such as a fluorocarbon or chlorofluorocarbon liquid, as areaction medium. Both scavenger and an inert liquid reaction medium canbe utilized, if desired. The fluorination is preferably carried out byliquid phase direct fluorination in the absence of hydrogen fluoridescavenger by using a temperature and inert gas flow rate sufficient tovolatilize hydrogen fluoride by-product and enable its removal from thefluorination zone as it is generated.

In another aspect, this invention provides a fluorochemical compositioncontaining the fluorinated ether acid or derivative thereof,hereinbefore described, as the sole essential component of thefluorochemical composition.

Although direct fluorination is a substitution method involving thereplacement of hydrogen atoms with fluorine, direct fluorinationprovides higher yields and purer products than do other substitutionmethods such as the electrochemical fluorination and cobalt trifluoridemethods—see, for example, U.S. Pat. No. 5,093,432 (Bierschenk et al.).The purity of the perfluorinated ether acid (or ester) compositions ofthe invention is further enhanced by the use of single precursorcompounds or selected (rather than random) mixtures thereof.

The preferred method of fluorination is the “liquid phase directfluorination technique,” which involves making a very dilute dispersionor, preferably, solution of the precursor(s) in a liquid reaction media,which is relatively inert to fluorine at the fluorination temperaturesused, the concentration of fluorinatable starting material thus beingrelatively low so as to more easily control the reaction temperature.The reaction mixture can also contain or have dispersed therein ahydrogen fluoride scavenger such as sodium fluoride, thescavenger:precursor weight ratio being, for example, from about 0.5:1 to7:1. The reaction mixture can be vigorously agitated while the fluorinegas is bubbled through it, the fluorine preferably being used inadmixture with an inert gas, such as nitrogen, at a concentration ofabout 5 to 50 volume %, more preferably about 10 to 25 volume %, andbeing maintained in stoichiometric excess throughout the fluorination,e.g., up to 15 to 40%, or higher, depending on the particular startingmaterial and the efficiency of the equipment used, such as the reactoragitation. Yields generally in the range of about 30-77 mole %, and,with experience, as high as 65 to about 85 mole %, of the perfluorinatedproduct may be achieved by this method.

Suitable liquids useful as reaction media for the liquid phase directfluorination technique are chlorofluorocarbons such as Freon™ 11fluorotrichloromethane; chlorofluoroethers; Fluorinert™ electronicliquids FC-75, FC-72, and FC-40; perfluoroalkanes such asperfluoropentane and perfluorodecalin; perfluoropolyethers; andperfluoroacetals. Mixtures of such liquids can be used, e.g., to getgood dispersion of precursor and intermediate reaction products. Thereaction media are conveniently used at atmospheric pressure. Lowermolecular weight members of the above classes of reaction media can alsobe used, but elevated pressures are then required to provide a liquidphase.

The liquid phase direct fluorination reaction is generally carried outat a temperature between about −10° C. to +50° C., preferably betweenabout −10° C. to 0° C. if a hydrogen fluoride scavenger is used, and, ifsuch a scavenger is not used, between about 0° C. to 150° C., preferablyabout 0° C. to 50° C., most preferably about 10° C. to 30° C., thetemperature being sufficient to volatilize the hydrogen fluorideby-product and, with the aid of the inert gas, flowing at a sufficientrates cause the purging of the by-product from the fluorination reactoras it is generated. At these temperatures, the liquids utilized asreaction media do not react appreciably with the diluted fluorine andare essentially inert. The reaction medium and other organic substancesmay to some extent be present in the gaseous reactor effluent, and acondenser may be used to condense the gaseous reaction medium and suchsubstances in the effluent and permit the condensate to return to thereactor. The condenser can be operated so as to minimize or prevent thereturn to the reactor of hydrogen fluoride by-product (which could havean adverse effect on yield of product if allowed to remain in thereactor during fluorination). The return of the hydrogen fluoride can beminimized or prevented by selective condensation of the organicmaterials while allowing the hydrogen fluoride to pass through thecondenser, or by total condensation of both hydrogen fluoride and theorganic materials into a separate vessel and followed, if desired, byseparation of the hydrogen fluoride as the upper liquid phase and thereturn of the lower liquid phase.

The liquid phase fluorination reaction may be carried out in a batchmode, in which all of the precursor is added to the liquid prior tofluorination to provide a precursor concentration of up to about 10% byweight, and the fluorine-containing gas is then bubbled through theprecursor-containing liquid. The reaction can also be carried out in asemi-continuous mode, in which the precursor is continuously pumped orotherwise fed neat, or as a diluted solution or dispersion, in asuitable liquid of the type used as a reaction medium, into the reactor,e.g., at a rate of about 1 to 3 g/hr into 400 mL of liquid reactionmixture, as fluorine is bubbled through, e.g., at a fluorine flow rateof about 40 to 120 mL/min and an inert gas flow rate of about 150 to 600mL/min. The fluorination can also be carried out in a continuous manner,in which the precursor (either neat or dissolved or dispersed in asuitable liquid of the type used as a reaction medium) is continuouslypumped or otherwise fed into the reactor containing the reaction ismedium as the fluorine-containing gas is introduced, as described above,and the stream of unreacted fluorine, hydrogen fluoride gas, and inertcarrier gas is continuously removed from the reactor, as is a stream ofliquid comprising perfluorinated product, incompletely fluorinatedprecursor, and inert liquid reaction medium, and the necessaryseparations are made to recover the fluoroalkyl ether composition. Ifdesired, the unreacted fluorine and the incompletely fluorinatedprecursor can be recycled. The amount of inert liquid medium in thereactor can be maintained at a constant level by addition of recycled orfresh liquid.

Due to the extremely high exothermicity of the fluorination reaction, acooled liquid or ice bath is generally employed in order that acceptablerates of reaction may be achieved. When the reaction is complete, thereactor is purged of fluorine and the reactor contents are removed.Where the fluorination is carried out by the liquid phase fluorinationtechnique in the presence of a hydrogen fluoride scavenger, the spentscavenger can be separated by filtration or decantation from the liquidreactor contents and the latter then distilled to separate the reactionmedium from the crude product. Where the fluorination is carried out bythe liquid phase fluorination technique without using the scavenger, thereaction product mixture can be distilled to recover the product.

Useful representative precursor fluorinatable ether acid esters whichcan be used to prepare the omega-hydrofluoroalkyl ethers of thisinvention are the hydrocarbon counterparts of the structures listed inTable A above, except that instead of the terminal hydrogen atom thestructures of the esters terminate with —Z′ (where Z′ is as defined forformula IV) or —CH₂OC(O)R (as shown in Scheme II supra) and that theprecursors can contain unsaturation.

Representative examples of the fluoroether acids of or used in thisinvention include the perfluorinated (i.e., having essentially allhydrogens replaced with fluorine) counterparts of the precursorfluorinatable acid esters described above. When the precursors haveunsaturation, the corresponding fluorinated ether acids are saturated.

As pointed out above, the fluoroether acids and derivatives can be usedas precursors in the preparation of the omega-hydrofluoroalkyl ethersand they are also useful, for example, as surfactants.

The above-described fluoroether acids or the esters thereof, e.g., alkylesters such as the methyl ester, can be converted by a decarboxylationprocess to the omega-hydrofluoroalkyl ethers of this invention. In onesuch process, a solution of KOH in ethylene glycol is prepared and thefluoroether acid or ester precursor is added thereto (neat or as asolution in an inert solvent liquid such as a perfluorinated liquid),preferably dropwise with stirring at ambient or room temperature. Theresulting mixture can then be heated slowly, for example, to 190° C.,during which time the methanol (from the saponification of a methylester), water (from neutralization of an acid), and decarboxylatedproduct are distilled. The omega-hydrofluoroalkyl ethers of theinvention are surprisingly stable under such harsh basic conditions. Aninert solvent liquid, if used, can be removed, for example, at lowtemperature under vacuum after neutralization. The resulting distillate,comprising the omega-hydrofluoroalkyl ether product, can be washed withwater, dried with silica gel or magnesium sulfate, and then distilled topurify the product. If desired, the hydrofluoroalkyl ether product canbe refluxed with a solution of potassium permanganate in acetone toremove easily-oxidized impurities. The yields of the ether product aregenerally high and the product generally will be quite pure and consistor consist essentially of the desired omega-hydrofluoroalkyl ether.

The omega-hydrofluoroalkyl ether compositions are non-toxic and capableof dissolving and transporting oxygen and are therefore potentiallyuseful as blood substitutes which can be employed invasively in thetreatment of trauma, vascular obstructions, as adjuvants to cancerradiation treatment or chemotherapy, and as imaging contrast agents. Forsuch uses, emulsions of the compositions can be prepared by methods suchas those described, for example, in U.S. Pat. No. 3,911,138 (Clark) andU.S. Pat. No. 5,077,036 (Long) and the PCT International Applicationpublished as WO 93/11868 (Kaufman et al.), which descriptions areincorporated herein by reference. The omega-hydrofluoroalkyl ethercompositions are also useful as solvents for cleaning and dryingapplications such as those described in U.S. Pat. No. 5,125,089 (Flynnet al.), U.S. Pat. No. 3,903,012 (Brandreth), and U.S. Pat. No.4,169,807 (Zuber). Minor amounts of optional components, e.g.,surfactants, may be added to the fluoroether compositions to impartparticular desired properties for particular uses. The ethercompositions are also useful as heat transfer agents or coolants inrefrigerator or freezer compressors or air conditioners, blowing agentsor cell size regulators in making polyurethane foam insulation, orchemical fire extinguishing agents in streaming applications, totalflooding, explosion suppression and inertion, and as carrier solventsfor highly fluorinated polyethers used as lubricants for magneticrecording media.

In using the omega-hydrofluoroalkyl ether compositions of this inventionfor the drying of or displacing water from the surface of articles, suchas circuit boards, the processes of drying or water displacementdescribed in U.S. Pat. No. 5,125,978 (Flynn et al.) can be used.Broadly, such process comprises contacting the surface of an articlewith a liquid composition comprising the ether composition of thisinvention, preferably in admixture with a non-ionic fluoroaliphaticsurface active agent. The wet article is immersed in the liquidcomposition and agitated therein, the displaced water is separated fromthe liquid composition, and the resulting water-free article is removedfrom the liquid composition. Further description of the process and thearticles which can be treated are found in said U.S. Pat. No. 5,125,978,which description is incorporated herein.

In using the ether composition of this invention as a heat transferliquid in vapor phase soldering, the process described in U.S. Pat. No.5,104,034 (Hansen) can be used, which description is incorporatedherein. Briefly, such process comprises immersing the component to besoldered in a body of vapor comprising the ether composition of thisinvention to melt the solder. In carrying out such a process, a liquidpool of the ether composition of this invention can be heated to boilingin a tank to form a saturated vapor in the space between the boilingliquid and a condensing means, a workpiece to be soldered is immersed inthe vapor whereby the vapor is condensed on the surface of the workpieceso as to melt and reflow the solder, and the soldered workpiece is thenremoved from the space containing the vapor.

In using the ether composition of this invention as a blowing agent inmaking plastic foam, such as foamed polyurethane, the process reactants,and reaction conditions described in U.S. Pat. No. 5,210,106 (Dams etal.) can be used, which description is incorporated herein. In carryingout such process, organic polyisocyanate and high molecular weightcompound with at least 2 reactive hydrogen atoms, such as a polyol, areadmixed in the presence of a blowing agent mixture comprising an ethercomposition of this invention, catalyst, and a surfactant.

This invention is further illustrated by the following examples, but theparticular materials and amounts thereof recited in these examples, aswell as other conditions and details, should not be construed to undulylimit this invention.

EXAMPLE 1 Preparation of C₈F₁₇—O—C₂F₄H from C₈F₁₇—O—C₂F₄CO₂CH₃

The organic starting material, C₈H₁₇—O—C₂H₄ CO₂CH₃, was prepared bybase-catalyzed Michael addition of n-octanol to acrylonitrile, followedby acid-catalyzed methanolysis. The methyl ester was directlyfluorinated with F₂ to produce the fluorinated ester,C₈F₁₇—O—C₂F₂CO₂CF₃. This fluorination was carried out in a 2-liter,jacketed reactor vessel of Monel™ metal equipped with a magnetic driveagitator, gas feed line, organic reactant feed line, and a refluxcondenser. The gas feed line was 0.3 cm diameter tube reaching to apoint below the bottom impeller of the agitator. The feed line was a0.15 cm diameter tube connected to a syringe pump. The reflux condenserconsisted of about 6-meters of two coiled concentric tubes, the innertube having a 1.27 cm diameter and the outer tube having a 2.54 cmdiameter. Gases from the reactor were cooled in the inner tube byrefrigerant, ethylene glycol-water, flowing in the annulus between thetwo tubes. The reactor was charged with about 1.8 liters of Freon™ 113chlorofluorocarbon and purged with 650 mL/min of nitrogen for 20minutes. The gas stream was then changed to a mixture of 310 mL/minfluorine and 1100 mL/min nitrogen. After about 12 minutes, 100 g ofC₈H₁₇—O—C₂H₄—CO₂CH₃, diluted to 260 mL with Freon™ 113chlorofluorocarbon, was fed to the reactor at a rate of 13 mL/hr (5 g/hrfeed rate). The reactor contents were maintained at about 16-18° C.throughout the fluorination. The condenser temperature was about −22° C.The fluorine flow was continued for ten minutes after complete additionof the organic feed. The reactor was then purged with nitrogen for onehour. The Freon™ 113 solution of the crude perfluorinated ester wastreated with 150 mL of 14% BF₃ in methanol and agitated vigorously for24 hrs. The mixture was washed with water, dried over MgSO₄ anddistilled (b.p. 40° C./0.2 torr) to yield C₈F₁₇—O—C₂F₄—CO₂CH₃ (47%yield). For purposes of decarboxylation, 39 g of 85% KOH was dissolvedin approximately 300 mL of ethylene glycol and the above-describedfluorinated methyl ester was added dropwise with stirring to the KOHsolution at room temperature. Upon complete addition, the reactionmixture had a pH of 8 to 9. The mixture was heated slowly with stirringand the product of decarboxylation, C₈F₁₇—O—C₂F₄H, was distilled alongwith methanol from saponification of the methyl ester, water from theKOH and a small amount of ethylene glycol. When the reaction mixturetemperature reached 170° C., the heating was stopped. The lowerfluorochemical phase of the distillate was separated, washed with water,dried and distilled through a three-plate Snyder column. The mainfraction, boiling at 146-150° C., yielded 122 g of product. Gaschromatography and mass spectrometry (GC/MS) of a sample of the productshowed the sample to be 94% pure and confirmed the structure asC₈F₁₇—O—C₂F₂H.

EXAMPLE 2 Preparation of C₈F₁₇—O—C₂F₄H from C₈F₁₇—O—C₂F₄CO₂H

C₈H₁₇—O—C₂H₄CO₂CH₃ was prepared by base-catalyzed Michael addition ofn-octanol to acrylonitrile, followed by acid-catalyzed methanolysis.This carboxylic acid ester was directly fluorinated by essentially thesame fluorination procedure described in Example 1 to produce thecorresponding ether acid, C₈F₁₇—O—C₂F₄COOH upon hydrolysis. Differentialscanning calorimetry revealed multiple transitions, which ischaracteristic of polymorphism.

A solution of 116 g of 85% KOH in 800 mL of ethylene glycol was preparedin a 3 L round-bottom flask. 1000 g of the C₈F₁₇OC₂F₄—CO₂H was addeddropwise to the stirred KOH solution. Upon complete addition, anadditional 10 g of KOH was added and the mixture heated. Thefluorochemical product of decarboxylation was distilled together with asmall amount of water from the neutralization of the acid. The lowerfluorochemical phase of the distillate was separated, washed with saltwater, dried over Na₂SO₄ and distilled as in Example 1 to yield 817 g ofC₈F₁₇—O—C₂F₄H.

EXAMPLE 3 Preparation of C₇F₁₅—O—C₂F₄H from C₇F₁₅—O—C₂F₄CO₂CH₃

C₇H₁₅—O—C₂H₄CO₂CH₃ was prepared by base-catalyzed Michael addition ofn-heptanol to acrylonitrile, followed by acid-catalyzed methanolysis.550 g of the corresponding methyl ester, C₇F₁₅—O—C₂F₄COOCH₃, (preparedby essentially the same fluorination and methanolysis procedures ofExample 1), was added dropwise to a solution of 166.6 g of KOH inapproximately 880 mL of ethylene glycol. The fluorochemical product wasrecovered essentially as in Example 1 to yield 440 g which was distilledthrough a six-plate Snyder column and the fraction boiling from 130 to131° C. was collected (340 g). This fraction was combined with 8.5 g ofKMnO₄ and approximately 350 g of acetone and heated to reflux. Afterfour hours, an additional 5 g of KMnO₄ was added and the resultingmixture was heated for an additional 3 hours. The mixture was filtered,the filter cake washed with acetone, and water was added to the filtratecausing a lower fluorochemical phase to form which was then washed withwater, followed by conc. H₂SO₄, again with water, and then filteredthrough silica. ¹H NMR and ¹⁹F NMR confirmed the reaction product tohave the desired structure, C₇F₁₅—O—C₂F₂H. Gas-liquid chromatography ofa sample showed it to be 98.7% pure.

EXAMPLE 4 Preparation of C₆F₁₃—O—C₂F₄—O—CF₂H fromC₆F₁₃—O—C₂F₄—OCF₂CO₂CH₃

The starting material, C₆H₁₃—O—C₂H₄—O—C₂H₄—O—COCH₃, was prepared byacetylation of hexyloxyethoxy ethanol with acetyl chloride. The acetatewas then converted to C₆F₁₃—O—C₂F₄—OCF₂CO₂CH₃ by essentially the samefluorination and methanolysis procedures of Example 1. 548 g of thisfluorochemical was combined with 144.2 g of KOH in 600 g of ethyleneglycol. The resulting mixture was heated, distilled and the product,C₆F₃—O—C₂F₄—OCF₂H, was recovered as in Example 1. Total yield was 433 g.The product was again distilled (b.p 131° C.) through a 12-inch (30.5cm) perforated-plate column at atmospheric pressure. The structure ofthe product was confirmed by ¹H and ¹⁹F NMR as C₆F₁₃—O—C₂F₄—OCF₂H. GC/MSrevealed a sample of it to be 99.6% pure.

EXAMPLE 5 Preparation of C₈F₁₇—O—CF₂H from C₈F₁₇—O—CF₂—CO₂CH₃

C₈H₁₇—O—C₂H₄—O—(CO)CF₃ was prepared by acetylation of octyloxyethanolwith trifluoroacetic anhydride. 100 g of the trifluoroacetate wasdirectly fluorinated by essentially the same fluorination procedures ofExample 1 and the fluorination product was quenched with a solution ofBF₃ in methanol to yield crude C₈F₁₇—O—CF₂—CO₂CH₃, which was furtherpurified by distillation, b. 92-97° C. @20 torr.

A 58 g sample of the latter methyl ester was decarboxylated using 10.8grams of KOH in ethylene glycol and the product, C₈F₁₇—O—CF₂H, wasrecovered as in Example 1. The structure of the product was confirmed by¹⁹F NMR. GLC revealed the product to be 99.6% pure, b. 134-136° C.

EXAMPLE 6 Preparation of C₄F₉—O—C₂F₄H from C₄F₉—O—C₂F₄—CO₂CH₃

The methyl ester, C₄H₉—O—C₂H₄—CO₂CH₃, was prepared by base-catalyzedMichael addition of n-butanol to acrylonitrile, followed byacid-catalyzed methanolysis. The methyl ester was then converted to thecorresponding fluorinated methyl ester, C₄F₉—O—CF₂CF₂—CO₂CH₃, byessentially the same fluorination and methanolysis procedures describedin Example 1.

1160 g of the latter methyl ester was added dropwise with stirring to3103 g of ethylene glycol and 129.5 g of NaOH. The product was distilled(b.p. 83° C.) and treated with KMnO₄/acetone, and worked up as inExample 3. The structure of the purified compound, C₄F₉—O—CF₂CF₂H, wasconfirmed by ¹H and ¹⁹F NMR and GC/MS.

A sample of this compound was evaluated for use in precision cleaningapplications by measuring the solubilities of selected hydrocarbonsolvents in the sample. High solubility would indicate improvedperformance as a cleaning agent relative to perfluorocarbon solvents Thefollowing hydrocarbon solvents were found to be soluble in amounts up to50% by weight with the ether hydride: hexane, heptane, toluene, acetone,2-butanone, 4-methyl-2-pentanone, ethyl acetate, methanol, ethanol,isopropanol, dimethyl formamide, trans-1,2-dichloroethylene andisopropyl ether. o-Xylene was found to be soluble to 19% by weight.Chloroform was found to be soluble to 45% by weight. Ethylene glycol wasfound to be soluble to less than 15% by weight and a light hydrocarbonoil was found to be soluble to less than 0.05% by weight.

A sample of the compound was also evaluated for use in spot-free dryingapplications such as taught in U.S. Pat. No. 5,125,978 (Flynn et al.). Awater displacement composition was prepared by dissolving 0.2% by weightof C₄F₉OC₂F₄OCF₂CONHC₂H₄OH in C₄F₉—O—C₂F₄H. The solution was heated to45° C. in an ultrasonic bath. Using the procedure described in U.S. Pat.No. 5,125,978, test coupons of glass and stainless steel were wettedwith water and subsequently immersed into this solution with ultrasonicagitation. All water was displaced within 60 seconds.

A sample of this compound was also evaluated for use as a rinse agent inco-solvent cleaning applications. (Such cleaning applications aretaught, for example, in International Patent Publication No. WO 92/22678(Petroferm Inc.). Organic esters such as methyl decanoate have foundutility as solvating agents in two-phase cleaning applications usingperfluorohexane as the carrier liquid and rinse agent.) Methyl decanoateand C₄F₉OC₂F₄H were placed in separate containers and heated to 50° C.in an ultrasonic bath. A 50 mm×25 mm×1.5 mm aluminum coupon wascontaminated with 0.0831 g of a light hydrocarbon oil. The contaminatedcoupon was first immersed in the methyl decanoate for about 60 secondsand then immersed in the C₄F₉OC₂F₄H for about 60 seconds. The C₄F₉OC₂F₄Hrinsed 100 percent (as determined by weight difference) of the oil andthe methyl decanoate from the coupon. Under the same conditions,perfluorohexane removed only 98.5 percent of the oil and methyldecanoate, indicating that C₄F₉OC₂F₄H can be more effective as a carrierliquid and rinse agent than perfluorohexane.

EXAMPLE 7 Preparation of HCF₂CF₂—O—CF₂CF₂—O—CF₂CF₂H fromCH₃OC(O)C₂F₄—O—C₂F₄—O—C₂F₄C(O)OCH₃

The starting material, CH₃OC(O)C₂H₄—O—C₂H₄—O—C₂H₄C(O)OCH₃, was preparedby base-catalyzed Michael addition of ethylene glycol to acrylonitrile,followed by acid-catalyzed methanolysis. The starting material was thenfluorinated and methanolysed by essentially the same proceduresdescribed in Example 1 to give CH₃OC(O)C₂F₄—O—C₂F₄—O—C₂F₄C(O)OCH₃.

1136 grams of the fluorinated ester was added to a mixture of 305.6 g ofKOH in 2665 g of ethylene glycol. The decarboxylation was carried outessentially as described in Example 1, and the crude product distilledafter phase separation but without water washing. The distillate stillcontained methanol which was removed by a wash with concentratedsulfuric acid followed by two water washes to give 695 g of the desiredether hydride product, with a boiling range of 93-94° C.

EXAMPLE 8 Preparation of C₄F₉—O—(CF₂)₅H from C₄F₉—O—(CF₂)₅—CO₂H

118.2 g (1.0 mol) hexane-1,6-diol, 4.4 g Adogen™ 464 quaternary ammoniumsalt, 80.0 g (2.0 mol) NaOH, and 250 mL tetrahydrofuran was stirred atreflux. 80 mL H₂O was added to get better mixing. After 20 min more, 137g (1.0 mol) butyl bromide was added over 0.5 hr, and stirred overnightat reflux. The reaction mixture was quenched in 1 L H₂O, and the upperlayer was combined with an ether extract of the lower layer, dried overMgSO₄, and stripped on a rotary evaporator. Treating the resultingstripped layer (151 g) in 100 mL CHCl₃ with 150 mL acetyl chloride addeddropwise and subsequently heating at reflux 4 hr and solvent removalgave 225.4 g of liquid. Distillation of the liquid gave 176.0 g (b.100-104° C./0.9 torr) of distillate. GLC indicated 56% of it to be thedesired 6-butoxyhexyl acetate, accompanied by hexanediol diacetate anddibutoxyhexane. 100 g of this mixture was fluorinated essentially as inExample 1. Treatment of the resulting fluorinated product with 30 mL ofa 10 weight percent solution of H₂SO₄ in H₂O and shaking at roomtemperature for 2 hours, filtration of solid fluorinated adipic acid,separation of the F-113 layer, drying over MgSO₄, and distillationproduced a main cut of 73.4 g, b. 116° C./20 torr, 96% pureC₄F₉—O—(CF₂)₅COOH. The latter was added to a solution of 10.0 g (0.25mol) NaOH and 100 mL ethylene glycol and the mixture was heated to 120°C., with C₄F₉—O(CF₂)₆—O—C₄F₉ impurity from fluorination collecting inthe Dean-Stark trap. On continued heating, gas evolution began and aliquid, C₄F₉—O(CF₂)₅H, (44.6 g) collected in the trap, ending by 170° C.The collected liquid was dried over silica gel and distilled on a 4-inch(10.2 cm) Vigreux column to 38.8 g, b.p 131° C. F-nmr confirmedstructure, in high purity, to be C₄F₉—O—(CF₂)₅H.

EXAMPLE 9 Preparation of C₅F₁₁—O—(CF₂)₅H from C₅F₁₁—O—(CF₂)₅COOH

In a similar fashion to Example 8, hexanediol was alkylated withn-pentyl bromide, the product was acetylated, and the crude acetate,C₅H₁₁—O—(CH₂)₆OC(O)CH₃, was distilled (b. 125° C./3 torr) and thedistillate was fluorinated essentially by the fluorination procedure ofExample 1. The fluorinated ester was hydrolyzed to the correspondingacid. Decarboxylation of the fluorinated acid, C₅F₁₁O(CF₂)₅COOH, withNaOH gave 829 g of product. The product was washed with water, driedover MgSO₄, and distilled to yield 555 g of C₅F₁₁—O—(CF₂)₅H, b. 145-149°C.

EXAMPLE 10 Preparation of C₈F₁₇—O—(CF₂)₅H from C₈F₁₇—O—(CF₂)₅COOH

In a fashion similar to Example 8, hexanediol was alkylated with n-octylbromide, the product was acetylated, and the resultingC₈H₁₇—O—(CH₂)₆—O—COCH₃ was directly fluorinated and hydrolyzed as inExample 8 to C₈F₁₇—O—(CF₂)₅COOH, which was recrystallized fromperfluorohexane. The recrystallized acid (37.5 g) was mixed with 4.0 gNaOH and 100 mL ethylene glycol and heated to 185° C. The product waswashed with water, and the residual 27.9 g was distilled to give pureC₈F₁₇—O—(CF₂)₅H, micro b.p. 195° C.

EXAMPLE 11 Preparation of C₄F₉—O—CF₂C(CF₃)₂CF₂H fromC₄F₉—O—CF₂C(CF₃)₂CF₂Cl

The alkylation of 2,2-dimethyl-1,3-propanediol with n-butyl bromidecarried out essentially as in Example 8 gave the crude mono-alkylatedproduct, which was treated with SOCl₂ to give C₄H₉—O—CH₂C(CH₃)₂CH₂Cl, b.80-90° C./20-30 torr. This compound was then fluorinated as in Example 1to give C₄F₉—O—CF₂C(CF₃)₂CF₂Cl. 20.0 g of the latter chloride was mixedwith 5.3 g water-wet Raney Ni and 50 mL of NH₃-saturated methanol. Themixture was left shaking on a Parr hydrogenation apparatus for 3 days atabout 25° C., with most of the 21 kPa (3 psig) hydrogen pressure dropoccurring in the first day. The product was recovered by filtration andquenched in water, yielding 7.9 g with some mechanical loss. ¹⁹F-nmrconfirmed the product to be C₄F₉—O—CF₂C (CF₃)₂CF₂H. A scaleup to 100 ggave 47 g, distilled to b.p 135° C.

EXAMPLE 12 Preparation of H(CF₂)₄—O—(CF₂)₄H from Cl(CF₂)₄—O—(CF₂)₄Cl

Cl—(CH₂)₄—O—(CH₂)₄—Cl was fluorinated as in Example 1 to provideCl(CF₂)₄—O—(CF₂)₄Cl. A mixture of 30.3 g Cl(CF₂)₄—O—(CF₂)₄Cl, 11.3 gfresh water-wet Raney Ni, and 200 mL methanol was purged for severalminutes with NH₃ and pressurized with 310 kPa (45 psig) hydrogen on aParr hydrogenation apparatus at about 25° C. After 17 hr, pressure haddropped to 255 kPa (37 psig) and the mixture had become acidic, withglass etching noted. More ammonia was added and the reduction wascontinued, dropping another 62 kPa (9 psig). The reaction product wasfiltered and quenched in water to give 15.4 g of lower phase, 68% pureproduct confirmed by GLC to be H(CF₂)₄—O—(CF₂)₄H. Distillation yielded27.0 g, b. 121-124° C., 87% pure.

EXAMPLE 13 Preparation of H(CF₂)₄—O—(CF₂)₄H and Cl(CF₂)₄—O—(CF₂)₄H fromCl(CF₂)₄—O—(CF₂)₄Cl

A mixture of 50.0 g Cl(CF₂)₄—O—(CF₂)₄Cl and 30 g Zn in butanol wasstirred at 110° C. for 2 days. GLC of a sample of the resulting reactionproduct indicated partial conversion. 21 g more Zn was added and themixture was heated one more day. Filtration and quenching of theresulting material in water gave 27.0 g of a colorless liquid. Theproduct was 35% of H(CF₂)₄—O—(CF₂)₄H, 42% mono hydride, and 16%unreduced dichloride.

EXAMPLE 14 Preparation of C₆F₁₃—O—CF₂CF₂H from C₆F₁₃—O—C₂F₄CO₂H

The starting material, C₆H₁₃—O—C₂H₄—CO₂CH₃, was prepared by the Michaeladdition of hexanol to acrylonitrile followed by acid-catalyzedesterification with methanol. The resulting ester was then fluorinatedand hydrolyzed to give the C₆F₁₃—O—C₂F₄CO₂H.

500 g of the acid C₆F₁₃—O—C₂F₄CO₂H, was added slowly to a solution of68.7 g KOH in 700 g ethylene glycol. At the end of the addition, anadditional 5 g of KOH was added to the homogeneous solution to bring thepH to 9. The decarboxylation was carried out as in Example 1 andsubsequently distilled, producing 327 g of product, b. 104-107° C. Theproduct was treated with potassium permanganate essentially as inExample 3. GC/MS, ¹⁹F nmr, ¹H nmr and IR confirmed structure of theproduct as C₆F₁₃—O—CF₂CF₂H.

EXAMPLE 15 Preparation of C₆F₁₃—O—CF₂H from C₆F₁₃—O—CF₂CO₂CH₃

The starting material, C₆H₁₃—O—C₂H₄OC(O)CH₃, prepared by acetylation ofethylene glycol monohexyl ether, was fluorinated and decarboxylated byessentially the procedures of Example 1 to give 146 g of C₆F₁₃—O—CF₂H(b. 92-96° C.).

EXAMPLE 16 Preparation of CF₃CF(CF₃)CF₂—O—CF₂H fromCF₃CF(CF₃)CF₂—O—CF₂CO₂CH₃

The starting material, CH₃CH(CH₃)CH₂—O—CH₂CH₂—OC(O)CH₃, was prepared byacetylation of ethylene glycol monoisobutyl ether and conversion byessentially the fluorination and methanolysis procedures of Example 1 togive the methyl ester, CF₃CF(CF₃)CF₂—O—CF₂CO₂CH₃, b. 118-120° C.

149 g of the methyl ester was added to 28.6 g of KOH in 700 g ofethylene glycol rapidly dropwise. The decarboxylation was carried out toafford, after distillation, the product cut, 70 g, b. 45-47° C., of 99%purity by GLC. The structure was confirmed by GC/MS, ¹H nmr, and ¹⁹F nmranalysis as CF₃—CF(CF₃)CF₂—O—CF₂H.

EXAMPLE 17 Preparation of C₄F₉—O—(CF₂)₄—O—(CF₂)₃H fromC₄F₉—O—(CF₂)₄—O—(CF₂)₃COOCH₃

The starting material, C₄H₉—O—C₄H₈—O—(CH₂)₃CH₂OCOCH₃, was directlyfluorinated and methanolysed essentially by the procedures of Example 1to produce C₄F₉—O—C₄F₈—O—(CF₂)₃CO₂CH₃. 56 g of the latter was addedrapidly to a solution of 5.6 g KOH in 250 ml of ethylene glycol. Thedecarboxylation was carried out and the product phase separated, washedonce with brine, and distilled to yield 36.6 g of product (b.p. 155-158°C.) of GLC purity 100%. GC/MS, ¹H, and ¹⁹F nmr analysis confirmed theproduct to be C₄F₉—O—(CF₂)₄—O—(CF₂)₃H.

EXAMPLE 18 Preparation of (C₂F₅)₂CFCF₂—O—C₂F₄H from(C₂F₅)₂CFCF₂—O—CF₂CF₂—C(O)OCH₃

Starting material, (C₂H₅)₂CHCH₂—O—CH₂CH₂C(O)OCH₃, prepared by theMichael addition of 2-ethylbutanol to acrylonitrile followed byacid-catalyzed esterification with methanol, was fluorinated andmethanolysed essentially by the procedures of Example 1 to give(C₂F₅)₂CFCF₂—O—CF₂CF₂—C(O)OCH₃, b.p. 159° C., the direct fluorinationyield, based on the methyl ester starting material being 88%.

The decarboxylation was carried out essentially as in Example 1 and theproduct distilled at 108-110° C. to yield 145 g, the IR analysis ofwhich was consistent with the structure (C₂F₅)₂CFCF₂—O—CF₂CF₂H.

EXAMPLE 19 Preparation of c—C₆F₁₁CF₂—O—C₂F₄H fromc—C₆F₁₁CF₂—O—C₂F₄C(O)OCH₃

The starting material, c—C₆H₁₁CH₂—O—C₂H₄C(O)OCH₃, prepared by thereaction of cyclohexylmethanol with acrylonitrile followed byacid-catalyzed esterification with methanol, was then fluorinated andmethanolysed with BF₃ in methanol by essentially the procedures ofExample 1 to give a 65% yield (based on the fluorination) ofc—C₆F₁₁CF₂—O—C₂F₄C(O)OCH₃.

224 g of the latter fluorinated ester was added to a solution of 28.2 gof 85% KOH and 466 g ethylene glycol held at 60° C. The resultingmixture was then heated to 100° C. and its pH adjusted to a pH greaterthan 7 by the addition of 5 g of 45 wt% aqueous KOH. Decarboxylation wascarried out by distillation of the resulting mixture. The lowerfluorochemical phase of the resulting distillate was separatedtherefrom, washed with an equal volume of water, and distilled at123-126° C. to give 155 g of a product (99.7% purity). The product wastreated with KMnO₄ in acetone to give c—C₆F₁₁CF₂—O—C₂F₄H.

EXAMPLE 20 Preparation of C₄F₉—O—C₂F₄—O—C₃F₆H fromC₄F₉—O—C₂F₄—O—C₃F₆C(O)OCH₃

C₄H₉—O—C₂H₄—O—C₄H₈OC(O)CH₃ was fluorinated and methanolysed byessentially the procedure of Example 1. The resulting product,C₄F₉—O—C₂F₄—O—C₃F₆C(O)OCH₃, in the amount of 419 g was rapidly addeddropwise to a mixture of 49.4 g KOH in 800 g ethylene glycol. Theresulting mixture was then heated slowly to a final flask temperature of190° C. During such heating, methanol from the saponification of theester, water, and C₄F₉—O—C₂F₄—O—C₃F₆H distilled from the reactionmixture. Water was added to the distillate and the lower, fluorochemicalphase (355 g) was separated and distilled (b. 120-122° C.) to provide308 g C₄F₉—O—C₂F₄—OC₃F₆H (82% yield).

EXAMPLE 21 Preparation of C₆F₁₃—O—C₄F₈—H from C₆F₁₃—O—C₄F₈—CO₂CH₃

The starting material, C₆H₁₃—O—C₅H₁₀—OC(O)CH₃, was prepared bymonoalkylation of 1,5-pentanediol with hexyl bromide, followed byacetylation with acetyl chloride. This compound was fluorinated andmethanolysed by essentially the procedure of Example 1, to giveC₆F₁₃—O—C₄F₈—CO₂CH₃, b.p 100° C. @ 13 torr. This ester wasdecarboxylated by heating a solution of 200 grams of ester in 250 mL ofethylene glycol with 30 g of KOH until the hydride product distilled.This liquid was washed with water, dried over MgSO₄ to give 128 g ofC₆F₁₃—O—C₄F₈—H of 82% purity. This was further purified by distillationusing a 12 plate packed glass column, b.p. 146° C. The structure wasconfirmed by ¹⁹F NMR.

EXAMPLE 22 Preparation of C₆F₁₃—O—C₃F₆—H from C₆F₁₃—O—C₃F₆—CO₂ ⁻K⁺

The starting material, C₆H₁₃—O—C₄H₈—OC(O)CH₃, was prepared bymonoalkylation of 1,4-butanediol with hexyl bromide , followed byacetylation with acetic anhydride. This compound was fluorinated andmethanolysed by essentially the procedure of Example 1, to giveC₆F₁₃—O—C₃F₆—CO₂CH₃. The methyl ester was saponified using excess KOH,and then dried in a vacuum oven to yield the potassium salt. 575 g ofthe salt was heated with stirring in 250 mL of ethylene glycol and theproduct hydride recovered from the distillate, b.p. 129° C. Thestructure was confirmed by ¹⁹F NMR.

EXAMPLE 23 Preparation of C₅F₁₁—O—C₄F₈—H from C₅F₁₁—O—C₄F₈—CO₂—Na⁺

The starting material, C₅H₁₁—O—C₅H₁₀—O—C(O)CH₃ was prepared bymonoalkylation of 1,5-pentanediol with pentyl bromide, followed byacetylation with acetyl chloride. This compound was fluorinated andmethanolysed by essentially the procedure of Example 1, to giveC₅F₁₁—O—C₄F₈—CO₂CH₃. The methyl ester was saponified using excess NaOH,and decarboxylated and distilled essentially as in Example 22.Distillation through a twelve-plate packed glass column gave pureC₅F₁₁—O—C₄F₈—H, b.p. 125° C. The structure was confirmed by ¹⁹F NMR.

EXAMPLE 24 Preparation of C₄F₉—O—C₃F₆—H from C₄F₉—O—C₃F₆-CO₂ ⁻Na⁺

The starting material, C₄H₉—O—C₄H₈—OC(O)CH₃, was prepared bymonoalkylation of 1,4-butanediol with butyl bromide, followed byacetylation with acetyl chloride. This compound was fluorinated andmethanolysed by essentially the procedure of Example 1, to giveC₄F₉—O—C₃F₆—CO₂CH₃. This methyl ester was saponified, decarboxylated andthe crude hydride recovered as in Example 23, and then further distilledto yield pure C₄F₉—O—C₃F₆—H , b.p. 90° C. The structure was confirmed by¹⁹F NMR.

EXAMPLE 25 Evaluation of Surfactant Activity of PerfluoroetherCarboxylic Acids

The surfactant activity of novel perfluoroether carboxylic acids of thisinvention was measured with a DeNuoy tensiometer after conversion of theacids to the corresponding ammonium salts. The acids were prepared bydirect fluorination of their hydrocarbon precursors, followed byhydrolysis. The ammonium salts were prepared by treatment of the acidwith excess aqueous ammonia followed by freeze drying. The results arereported in dynes/cm in the following Table C which lists the parentacid (from Table B) of the ammonium salt.

TABLE C Surface Tension (dynes/cm) Melting Concentration of AmmoniumSalt Parent Acid Point(s) of 50 100 500 1000 from Table B Acid (°C.) ppmppm ppm ppm 18 −1 24 21 18 2 21 24 4 63 59 39 29 5 33 33 26 22 7 19 3726 19 17 6 31 23 18 17 8 33 31 26 24 9 38 24 20 18 10 38 35 24 19 27 −3967 63 50 43 29 −9 49 43 29 23 35 18 18 16 16 25 −9 19 15 15 14 30 46 4332 24 31 69 68 48 52 32 63 54 31 21 33 28 21 15 40 48 41 23 19 11 49,5918 15 15 14 39 31 18 15 16,−27 30 17 17 16 24 19 18 17 17 90 14 15 15

EXAMPLE 26 Evaluation of Ethers as Fire Extinguishing Agents

Omega-hydrofluoroalkyl ether compounds of this invention were evaluatedas fire extinguishing agents using the National Fire ProtectionAssociation 2001 Fire Protection Standard, with a cup burner modified tohandle liquid compounds. The results, shown below in Table D, indicatethat the compounds could be effective agents for fire extinguishing,explosion suppression, and as flammable atmosphere inerting agents.

TABLE D Extinguishment Agent concentration, vol. % C₄F₉OC₂F₄H 5.6HC₃F₆OC₃F₆H 5.7

EXAMPLE 27 Preparation of Foamed Polyurethane

Omega-hydrofluoralkyl ether compounds of this invention were evaluatedas blowing agents for foams using the procedures taught in U.S. Pat. No.5,210,106 (Dams et al.). Component A contained 15.0 parts by weight ofPAPI™27, a methylene diphenyldiisocyanate having an isocyanateequivalent of 134.0, available from Dow Chemical. Component B of thefoam contained 10.5 parts by weight (pbw) of Voranol™ 360, a polyetherpolyol with a hydroxyl number of 360 available from Dow Chemical; 0.26pbw of water; 0.26 pbw of an oligomeric fluorochemical surfactant asdescribed in Example 1 of U.S. Pat. No. 3,787,351; 0.13 pbw of Polycat™8, a N,N-dimethylcyclohexylamine catalyst available from Air Products;and 1.87 pbw of C₄F₉OCF₂CF₂H as the blowing agent.

The ingredients of Component B were mixed to obtain an emulsion whichwas then admixed with Component A and stirred at 2500 rpm for 10seconds. The cream time of the foam was approximately 10 seconds. Risetime and tack-free time was approximately 2 and 3 minutes respectively.The resulting polyurethane foam was rigid and had a uniform distributionof very fine, closed cells.

EXAMPLE 28 Preparation of (CF₃)₃COC₂F₄OCF₂OCF₂CO₂CH₃.

The precursor, (t-C₄H₉OC₂H₄O)₂CH₂, prepared by alkylation of methylenechloride with t-butoxy ethanol, was fluorinated and methanolysedessentially as in Example 1 to yield (CF₃)₃COC₂F₄OCF₂OCF₂CO₂CH₃, havinga boiling range 80-82° C. at 18 torr, and whose structure was confirmedby ¹⁹F NMR.

EXAMPLE 29 Preparation of C₈F₁₇OCF₂OC₃F₆H from C₈F₁₇OCF₂OC₃F₆CO₂CH₃.

The precursor, C₈H₁₇OCH₂OC₄H₈OH was prepared by monoalkylation of butanediol with octyl chloromethyl ether. The precursor was first acetylatedwith acetyl chloride in methylene chloride containing triethylamine andthen fluorinated, and a portion of the crude perfluorinated product washydrolyzed by treatment with aqueous sulfuric acid and then distilled toyield the carboxylic acid C₈F₁₇OCF₂OC₃F₆CO₂H, having a boiling range100-106° C. at 1.1 torr. Differential scanning calorimetry revealed theacid had a T_(g) of −97.0° C. and several crystalline exotherms of−77.4, −61.5 and −37.7° C. and a broad melting point at −9.0° C.

Another portion of the crude perfluorinated products was methanolysedessentially as in Example 1 to yield C₈F₁₇OCF₂OC₃F₆CO₂CH₃, having aboiling range 124-130° C. at 25 torr. The latter methyl ester was thendecarboxylated using the procedure of Example 1 to yieldC₈F₁₇OCF₂OC₃F₆H, having a boiling range of 178-183° C.; the structuresof this hydride and the precursor fluorinated ester were confirmed by¹⁹F NMR.

EXAMPLE 30 Preparation of C₈F₁₇O—(C₂F₄O)₂CF₂CO₂H.

The precursor was prepared by monoalkylation of triethylene glycol withoctyl bromide, followed by acetylation. The precursor was fluorinated asin Example 1, hydrolyzed by treatment with aqueous sulfuric acid, anddistilled, the product, C₈F₁₇O—(C₂F₄O)₂CF₂CO₂H, having a boiling rangeof 105-110° C. at 1.4 torr, and a melting point of 24° C.

EXAMPLE 31 Preparation of HC₃F₆OC₃F₆H from CH₃O(CO)C₃F₆OC₃F₆COOCH₃

The starting diacetate, CH₃C(O)OC₄H₈O—(C₄H₈₉O)_(n)C₄H₈OC(O)CH₃, wasprepared by acetylation of polytetramethylene glycol (average molecularweight of 250) with acetyl chloride. The diacetate was then converted toCH₃OC(O)C₃F₆O—(C₄F₈O)_(n)C₃F₆COOCH₃ by essentially the same fluorinationand methanolysis procedures described in Example 1. 1400 g of theresulting mixture of diesters was distilled on a ten-plate glass-packedcolumn to isolate CH₃OC(O)C₃F₆OC₃F₆COOCH₃.

278 g of the isolated fluorochemical was combined with 72 g of KOH in250 mL of ethylene glycol. The resulting mixture was heated, distilled,and the product, HC₃F₆OC₃F₆H, was recovered essentially as in Example 1(b.p. 84° C.). The structure of the product was confirmed by ¹⁹F NMR.

EXAMPLE 32 Preparation of n—C₁₂F₂F₂₅OC₂F₄OC₂F₄OCF₂CO₂H.

The precursor, n—C₁₂H₂₅O(C₂H₄O)₃H, was prepared by monoalkylation oftriethylene glycol with n-dodecyl bromide. After acetylation, theresulting product was fluorinated essentially as in Example 1, and thefluorinated product was concentrated and treated with 55.0 g NaOH in 300mL water. After heating for 5 hours on a steam bath, the product wasacidified with an excess of a 50 weight percent solution of H₂SO₄ inwater and then extracted with Fluorinert™ FC-75 perfluorinated liquid (amixture of C₈ perfluorochemicals, b.p. 103° C.) which had been heated toabout 60° C. on a steam bath. Distillation yielded puren—C₁₂F₂₅OC₂F₄OC₂F₄OCF₂CO₂H(T_(g)=−62.7° C. and T_(m)=69.2° C. by DSC).

EXAMPLE 33 Preparation of

The starting material, methyl 2-(3,4-dimethoxyphenyl)acetate wasfluorinated essentially as in Example 1 to yieldperfluoro-2-(3,4-dimethoxycyclohexyl)acetic acid after hydrolysis. Thiswas then decarboxylated essentially as described in Example 1 to theperfluorinated ether hydride.

EXAMPLE 34 Preparation of

The starting material, methyl 3-(4-ethoxyphenyl)-trans-2-propenoate wasprepared by condensation of 4-ethoxybenzaldehyde with malonic acid,followed by esterification. This methyl ester was fluorinated,methanolized, and decarboxylated essentially as in Example 1 to producethe perfluorinated ether hydride.

EXAMPLE 35 Preparation of

The starting material was prepared by condensation of 2,2-diethylpropane diol with dimethyl 3-oxoglutarate. This dimethyl ester wasfluorinated, methanolyzed to the diester, and decarboxylated essentiallyas in Example 1 to produce the perfluorinated ether dihydride.

EXAMPLE 36 Preparation of

The starting material was prepared by reaction of 2,6-dimethylphenolwith ethylene carbonate and subsequent acetylation with acetyl chloride.This acetate was fluorinated, methanolyzed, and decarboxylatedessentially as in Example 1 to produce the perfluorinated ether hydride(b.p. 132° C.).

EXAMPLE 37 Preparation of

The starting material was prepared by the treatment of2-(2,6-dimethylphenyloxy)ethanol (from Example 36) with thionylchloride. This was fluorinated essentially as in Example 1, followed byRaney Ni reduction of the chloride essentially as described in Example12 to produce the perfluorinated ether hydride.

EXAMPLE 38 Preparation of

The starting material was prepared from the addition of β-napthol toethylene carbonate, followed by acetylation with acetyl chloride. Thisacetate was fluorinated, methanolyzed, and decarboxylated essentially asin Example 1 to produce the perfluorinated ether hydride (b.p. 171° C.).

EXAMPLE 39 Preparation of C₅F₁₁OCF₂C(CF₃)₂CF₂H fromC₅H₁₁OCH₂C(CH₃)₂CH₂Cl

The starting material was prepared essentially as described above inExample 11. The ether chloride was fluorinated essentially as in Example1, followed by Raney Ni reduction of the chloride essentially asdescribed in Example 11 to produce the perfluorinated ether hydride(b.p. 148° C.).

EXAMPLE 40 Preparation of (C₄F₉O)₂CFCF₂H from (C₄H₉O)₂CHCH₂Cl

The starting material was prepared by the addition of n-butanol to2-chloroacetaldehyde and was fluorinated essentially as in Example 1,followed by Raney Ni reduction of the chloride essentially as describedin Example 11 to produce the perfluorinated ether hydride.

EXAMPLE 41 Preparation of CF₃O(CF₂)₉H from CH₃O(CH₂)₁₀OAc

The starting material was prepared by monoalkylation of 1,10-decanediolwith dimethyl sulfate, followed by acetylation with acetyl chloride.This acetate was fluorinated, hydrolyzed, and decarboxylated essentiallyas in Example 1 to produce the perfluorinated ether hydride.

EXAMPLE 42 Preparation of C₉F₁₉OCF₂H from C₉H₁₉OC₂H₄OAc

The starting material was prepared by monoalkylation of ethylene glycolwith n-nonyl bromide, followed by acetylation with acetyl chloride. Thisacetate was fluorinated, hydrolyzed, and decarboxylated essentially asin Example 1 to produce the perfluorinated ether hydride (b.p. 155° C.).

EXAMPLE 43 Preparation of (iso-C₃F₇)₂CFOC₂F₄H from(iso-C₃H₇)₂CHOC₂H₄CO₂CH₃

The starting material was prepared by Michael addition of2,4-dimethyl-3-pentanol to acrylonitrile, followed by methanolysis tothe methyl ester. This ester was fluorinated, hydrolyzed, anddecarboxylated essentially as in Example 1 to produce the perfluorinatedether hydride.

EXAMPLE 44 Preparation of

The starting material was prepared by the alkylation of 4-ethylphenolwith methyl chloroacetate. This ester was fluorinated, hydrolyzed, anddecarboxylated essentially as in Example 1 to produce the perfluorinatedether hydride (b.p. 131° C.).

EXAMPLE 45 Comparative Atmospheric Lifetimes and Boiling Points

The atmospheric lifetime of various sample compounds was calculated bythe technique described in Y. Tang, Atmospheric Fate of VariousFluorocarbons, M. S. Thesis, Massachusetts Institute of Technology(1993). As shown in the table below, the atmospheric lifetime of anether hydride compound having two or more carbon atoms between the etheroxygen atom and the terminal hydrogen atom is considerably shorter thanthe atmospheric lifetimes of ether hydride compounds having only onecarbon atom between the ether oxygen atom and the terminal hydrogenatom. Because of the shorter atmospheric lifetimes of the compounds ofthe present invention, these compounds are more environmentallyacceptable.

Atmospheric Lifetime Compound (yrs) C₆F₁₃OC₂F₄OCF₂H >170C₄F₉OC₂F₄OCF₂H >170 C₈F₁₇OCF₂CF₂H 80

In addition, as shown in the table below, ether hydride compounds havingtwo or more carbon atoms between the ether oxygen atom and the terminalhydrogen atom have lower boiling points than analogous non-ethercompounds, and significantly lower boiling points than analogous etherhydride compounds having only one carbon atom between the ether oxygenatom and the terminal hydrogen atom. The unexpectedly low boiling pointsof compounds of the present invention render the compounds useful inprocesses involving temperature-sensitive substrates such as plastics.(For example, in vapor-phase cleaning, a substrate is rinsed in thecondensing vapor of a boiling fluid, and in condensation heating, asubstrate is heated by immersion in a boiling fluid.) In suchapplications, a lower-boiling fluid is preferred so as to avoid damageto the substrate. While it is known that boiling points can be reducedby selection of a compound having fewer carbon atoms, this may result ina boiling point reduction of 25° C. or more, in addition to adverselyaffecting other properties such as solvency.

Boiling Point Compound (° C.) C₈F₁₇CF₂H 136 C₈F₁₇OCF₂H 139 C₇F₁₅OC₂F₄H131

126

134

131

125 C₉F₁₉CF₂H 154 C₉F₁₉OCF₂H 155 C₈F₁₇OC₂F₄H 148 C₆F₁₃OC₄F₈H 149C₅F₁₁OC₅F₁₀H 150

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

What is claimed is:
 1. A process for transferring heat comprising thestep of transferring heat between a heat source and a heat sink throughthe use of a heat transfer agent comprising at least one normally liquidomega-hydrofluoroalkyl ether compound having a saturatedperfluoroaliphatic chain of carbon atoms interrupted by one or moreether oxygen atoms, the chain carbon atom at one end (the proximal end)of the chain being that of a difluoromethyl group which is bonded toanother chain carbon atom or to a said ether-oxygen atom, the carbonatom at the other end (the distal end) of the chain being part of adistal group selected from the group consisting of difluoromethyl,difluorochloromethyl, a straight-chain perfluoroalkyl, a branched-chainperfluoroalkyl, and a perfluoroalkyl substituted with a saturatedperfluoroalicyclic moiety, with the proviso that where saiddifluoromethyl group at the proximal end is bonded to a saidether-oxygen atom, then said straight-chain perfluoroalkyl has at least6 chain carbon atoms and said branched-chain perfluoroalkyl has at least4 carbon atoms.
 2. The process of claim 1 wherein said normally liquidomega-hydrofluoroalkyl ether compound is represented by the generalformula: X—R_(f)—O—(R_(f)′—O)_(n)—R_(f)″—H wherein: H is a primaryhydrogen atom; X is a fluorine atom, a primary hydrogen atom, or aprimary chlorine atom; n is an integer of 0 to 7; and R_(f), R_(f)′, andR_(f)″ are independently selected from the group consisting of linear orbranched, unsubstituted perfluoroalkylene groups; linear or branched,perfluoroalkyl- or perfluorocycloalkyl-substituted perfluoroalkylenegroups; and linear or branched perfluoroalkylene groups substituted withan ether oxygen-containing moiety; with the proviso that when X is H orCl, R_(f) has 1 to 18 chain carbon atoms, R_(f)′ has 1 to 12 chaincarbon atoms, and R_(f)″ has 2 to 12 chain carbon atoms; and with thefurther proviso that when X is F, then R_(f) has at least 4 chain carbonatoms, R_(f)′ has 1 or more chain carbon atoms, and R_(f)″ has 2 or morechain carbon atoms.
 3. The process of claim 2 wherein said X is afluorine atom.
 4. The process of claim 2 wherein said normally liquidomega-hydrofluoroalkyl ether compound is represented by the formula:X—R_(f)—O—(CF₂CF₂—O)_(m)—R_(f)″—H where m is an integer of 0 to 7, andH, X, R_(f), and R_(f)″ are as defined in claim
 12. 5. The process ofclaim 2 wherein said normally liquid omega-hydrofluoroalkyl ethercompound is represented by the formula:F—R_(f)—O—(R_(f)′—O)_(p)—R_(f)″—H where p is an integer of 0 to 2, andH, R_(f), R_(f)″, and R_(f)″ are as defined in claim 12, except thatR_(f) has 4 to 12 chain carbon atoms, R_(f)′ has 1 to 12 chain carbonatoms, and R_(f)″ has 2 to 12 chain carbon atoms.
 6. The process ofclaim 2 wherein said normally liquid omega-hydrofluoroalkyl ethercompound is represented by a formula selected from the group consistingof C₈F₁₇—O—C₂F₄H, C₇F₁₅—O—C₂F₄H, C₆F₁₃—O—C₂F₄—O—CF₂H, C₄F₉—O—C₂F₄H,HCF₂CF₂—O—CF₂CF₂—O—CF₂CF₂H, C₄F₉—O—(CF₂)₅H, C₅F₁₁—O—(CF₂)₅H,C₈F₁₇—O—(CF₂)₅H, C₄F₉—O—CF₂C(CF₃)₂CF₂H, H(CF₂)₄—O—(CF₂)₄H,Cl(CF₂)₄—O—(CF₂)₄H, C₆F₁₃—O—C₂F₄H C₄F₉—O—(CF₂)₄—O—(CF₂)₃H,(C₂F₅)₂CFCF₂—O—C₂F₄H, c—C₆F₁₁CF₂—O—C₂F₄H, C₄F₉—O—C₂F₄—O—C₃F₆H,C₆F₁₃—O—C₄F₈H, C₆F₁₃—O—C₃F₆H, C₅F₁₁—O—(CF₂)₄H, C₄F₉—O—C₃F₆H,C₈F₁₇OCF₂OC₃F₆H, HC₃F₆OC₃F₆H,

C₅F₁₁OCF₂C(CF₃)₂CF₂H, (C₄F₉O)₂CFCF₂H, CF₃O(CF₂)₉H, and(iso-C₃F₇)₂CFOC₂F₄H.
 7. The process of claim 1 wherein said normallyliquid omega-hydrofluoroalkyl ether compound is represented by thegeneral formula: X—R_(f)—O—(R_(f)′—O)_(n)—R_(f)″—H wherein: H is aprimary hydrogen atom; X is a fluorine atom, a primary hydrogen atom, ora primary chlorine atom; n is an integer of 0 to 7; and R_(f), R_(f)′,and R_(f)″ are independently selected from the group consisting oflinear or branched, unsubstituted perfluoroalkylene groups; linear orbranched, perfluoroalkyl- or perfluorocycloalkyl-substitutedperfluoroalkylene groups; and linear or branched perfluoroalkylenegroups substituted with an ether oxygen-containing moiety; with theproviso that when X is H or Cl, R_(f) has 1 to 18 chain carbon atoms andeach of R_(f)′ and R_(f)″ independently has 1 to 12 chain carbon atoms;and with the further proviso that when X is F, then R_(f) has at least 4chain carbon atoms, and each of R_(f)′ and R_(f)″ independently has 1 ormore chain carbon atoms; and with the still further proviso that when nis zero, then R_(f) is a perfluorocycloalkyl-substitutedperfluoroalkylene group.